1. Field of the Invention
The present invention relates generally to medical devices and methods. In particular, the present invention relates to an oral device that may be held in the mouth of a patient to reduce the incidence of obstructive sleep apnea or snoring.
Obstructive sleep apnea (OSA) is a serious medical condition resulting from a temporary airway blockage which occurs as a patient sleeps. The airway blockage usually occurs between the soft palate and/or the back of the tongue and the pharynx. As the patient breathes, the reduced area in the upper airway can cause snoring, and more seriously, OSA. Sleep disruption caused by OSA can result in severe daytime sleepiness, chronic fatigue, headaches, depression, accidents, injuries, and of particular concern, OSA can reduce the amount of oxygen entering the lungs causing hypoxia. Hypoxia, in turn, can lead to pulmonary hypertension, heart disease, and stroke.
Numerous invasive and less invasive treatments have been proposed for OSA. Of particular interest to the present invention, “continuous positive airway pressure” (CPAP) delivers a continuous stream of pressurized air directly to the person's upper airway. The positive pressure maintains patency of the airway and inhibits the collapse associated with OSA. Although generally effective, CPAP suffers from a number of drawbacks that have led to a high level of non-compliance. The patient must wear a bulky facial mask which can be uncomfortable, and the system generates noise that can make falling asleep difficult. CPAP is also difficult to use because the mask requires careful fitting to avoid air leaks and facial discomfort and because the mask can easily be dislodged during sleep. Moreover, a number of unpleasant side effects, such as sore throats, dry throat and eyes, headaches, and skin rashes from the mask frequently occur. These problems have resulted in a high level of non-compliance with CPAP therapy.
As an improvement over CPAP, it has been proposed to apply a negative pressure to the forward end of the patient's mouth, typically at or just behind the lips, to pull the tongue forward in order to lift the rear portion of the tongue away from the back of the airway. See, for example, U.S. Pat. Nos. 6,494,209 and 7,328,698, and U.S. Patent Publication Nos. 2011/0259346; 2007/0277818; 2005/0166928 and 2005/0166929. While promising in theory, in practice it is very difficult to apply a vacuum in the region of the tip of the tongue to raise the base of the tongue and clear the patient's airway, particularly when the patient is lying on his or her back and gravity is pulling the tongue posteriorly. The tongue is a relatively large and compliant organ with significant mass, and applying a vacuum over a relatively small surface area at the tip will often not be effective in raising the back of the tongue against gravity. The moist and compliant tissues in the mouth are somewhat self-sealing, and this effect tends to inhibit the propagation of negative pressure, thereby confining the negative pressures to a relatively small area near the point of application. Thus, simply applying a vacuum at a location near the anterior tip of the tongue tends to draw the tongue up against the hard palate posterior to this location, creating a seal that restricts the propagation of vacuum through this region of contact toward the back of the oral cavity, where direct vacuum is usually required for maximum effectiveness.
As another improvement over CPAP, it has been proposed to place various devices in direct contact with the posterior tissues of the mouth such as the soft palate and posterior portions of the tongue. A major disadvantage of these approaches is that contact with certain tissues near the posterior area of the tongue may elicit the gag reflex and in any case the presence of such devices so far back in the mouth can be uncomfortable.
Still further improvements in the treatment of sleep apnea are described in U.S. Pat. Nos. 8,074,656; 8,074,656; and 8,122,889, and U.S. Patent Publication 2012/0017917, assigned to the assignee of the present application, the full disclosures of which are incorporated herein by reference. These patents describe engaging a lateral element across a medial region of the tongue to create a clearance above the tongue. By drawing a vacuum in the clearance, the soft palate can be drawn forward to open the airway. While very successful in many patients, the treatment is not fully effective in some patients.
For these reasons, it would be desirable to provide alternative and improved methods and apparatus for treating obstructive sleep apnea and snoring. The methods and devices should be non-invasive and require no surgery or permanently implanted components. In addition, the methods and devices should be minimally intrusive with components that are comfortable and quiet so that disruption of the patient's sleep is minimized. Moreover, the methods and devices should avoid contacting the portions of the oral cavity that trigger the gag reflex. The methods and systems should also be simple to implement and be effective to significantly improve patency of a patient's airway during sleep in a broad population of patients suffering from sleep apnea. At least some of these objectives will be met by the inventions described hereinafter.
2. Description of the Background Art
U.S. Pat. Nos. 8,074,656; 8,122,889; and 8,122,890, and U.S. Patent Publication Nos. 2012/007917 and 2012/0199135, assigned to the assignee of the present application, describe oral appliances for engaging a medial region of a patient's tongue to maintain airway patency. U.S. Pat. Nos. 6,595,209 and 7,328,698, and U.S. Patent Publication No. 2011/0259345, oral appliances for applying a vacuum to pull an anterior region of a patient's tongue forward to treat sleep apnea. See also Tsuiki et al. (2012) AM. J. Respir. Crit. Care Med. 185: A6461.